WASHINGTON - US President Barack Obama urged Americans on Saturday to recall the spirit that united the country after the September 11 attacks and take part in a national day of service to mark the anniversary next month.

In remarks acknowledging the "great challenges" that confront the US economy, and could hurt his reelection chances next year, Obama also sought to rise above the partisan political rancor that has divided Washington all summer.

"As we mark this solemn anniversary, let's summon that spirit once more. And let's show that the sense of common purpose that we need in America doesn't have to be a fleeting moment; it can be a lasting virtue," Obama said in his weekly radio address.

With US unemployment stuck above 9 percent, Democrat Obama is fighting for more measures to boost growth and hiring but has been thwarted so far by Republicans in Congress, who control the US House of Representatives.

He will unveil a package of employment-creating measures in a major jobs speech after the September 5 Labor Day holiday which White House aides say will contain a number of new proposals.

Obama and his wife Michelle will mark the 10th anniversary of the attacks by visiting Ground Zero in New York, the Pentagon, and the site in Shanksville, Pennsylvania, where the fourth hijacked airline crashed after its passengers .

"But even if you can't be in New York, Pennsylvania or Virginia, every American can be part of this anniversary. Once again, 9/11 will be a National Day of Service and Remembrance," Obama said.

The attacks, blamed on Osama bin Laden's al Qaeda extremist network, killed nearly 3,000 people in September 2001. Bin Laden was killed earlier this year in an attack on his compound in Pakistan and his network has been splintered and weakened by repeated attacks by allied western forces in recent years.